关键词：PLC，编程语言，温度
Abstract
The programmable logic controller (PLC) was developed in 1968. PLC is a solid-state device used to control machine motion or process operation by means of a stared program .The PLC sends output control signals and receives input signals through input/out (I/O) devices. PLC design is for bad industrial environmental use. Because of the comprehensive computer and automatic technology， make its development change with each passing day， exceed the engineering level while it appears greatly. It can finish logic， order， timing， count， digital operation， data processing， etc. function very easily， and can establish with all kinds of connection with analog quantity of amount of mechanical figure produced through the input-output interface， thus realize the automatic control of the production process. Especially the rapid development， information， arrival of cyber times of the very large scale integration， expanded the function of PLC， makes it have very strong networking communication ability， thus widely apply to numerous trades even more. The temperature supervisory system that this paper is concerned with can the temperature of monitoring send， and can the control on-the-spot with control through computer.
